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common/multiprocessing_env.py

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+#This code is from openai baseline
+#https://github.com/openai/baselines/tree/master/baselines/common/vec_env
+
+import numpy as np
+from multiprocessing import Process, Pipe
+
+def worker(remote, parent_remote, env_fn_wrapper):
+    parent_remote.close()
+    env = env_fn_wrapper.x()
+    while True:
+        cmd, data = remote.recv()
+        if cmd == 'step':
+            ob, reward, done, info = env.step(data)
+            if done:
+                ob = env.reset()
+            remote.send((ob, reward, done, info))
+        elif cmd == 'reset':
+            ob = env.reset()
+            remote.send(ob)
+        elif cmd == 'reset_task':
+            ob = env.reset_task()
+            remote.send(ob)
+        elif cmd == 'close':
+            remote.close()
+            break
+        elif cmd == 'get_spaces':
+            remote.send((env.observation_space, env.action_space))
+        else:
+            raise NotImplementedError
+
+class VecEnv(object):
+    """
+    An abstract asynchronous, vectorized environment.
+    """
+    def __init__(self, num_envs, observation_space, action_space):
+        self.num_envs = num_envs
+        self.observation_space = observation_space
+        self.action_space = action_space
+
+    def reset(self):
+        """
+        Reset all the environments and return an array of
+        observations, or a tuple of observation arrays.
+        If step_async is still doing work, that work will
+        be cancelled and step_wait() should not be called
+        until step_async() is invoked again.
+        """
+        pass
+
+    def step_async(self, actions):
+        """
+        Tell all the environments to start taking a step
+        with the given actions.
+        Call step_wait() to get the results of the step.
+        You should not call this if a step_async run is
+        already pending.
+        """
+        pass
+
+    def step_wait(self):
+        """
+        Wait for the step taken with step_async().
+        Returns (obs, rews, dones, infos):
+         - obs: an array of observations, or a tuple of
+                arrays of observations.
+         - rews: an array of rewards
+         - dones: an array of "episode done" booleans
+         - infos: a sequence of info objects
+        """
+        pass
+
+    def close(self):
+        """
+        Clean up the environments' resources.
+        """
+        pass
+
+    def step(self, actions):
+        self.step_async(actions)
+        return self.step_wait()
+
+
+class CloudpickleWrapper(object):
+    """
+    Uses cloudpickle to serialize contents (otherwise multiprocessing tries to use pickle)
+    """
+    def __init__(self, x):
+        self.x = x
+    def __getstate__(self):
+        import cloudpickle
+        return cloudpickle.dumps(self.x)
+    def __setstate__(self, ob):
+        import pickle
+        self.x = pickle.loads(ob)
+
+
+class SubprocVecEnv(VecEnv):
+    def __init__(self, env_fns, spaces=None):
+        """
+        envs: list of gym environments to run in subprocesses
+        """
+        self.waiting = False
+        self.closed = False
+        nenvs = len(env_fns)
+        self.nenvs = nenvs
+        self.remotes, self.work_remotes = zip(*[Pipe() for _ in range(nenvs)])
+        self.ps = [Process(target=worker, args=(work_remote, remote, CloudpickleWrapper(env_fn)))
+            for (work_remote, remote, env_fn) in zip(self.work_remotes, self.remotes, env_fns)]
+        for p in self.ps:
+            p.daemon = True # if the main process crashes, we should not cause things to hang
+            p.start()
+        for remote in self.work_remotes:
+            remote.close()
+
+        self.remotes[0].send(('get_spaces', None))
+        observation_space, action_space = self.remotes[0].recv()
+        VecEnv.__init__(self, len(env_fns), observation_space, action_space)
+
+    def step_async(self, actions):
+        for remote, action in zip(self.remotes, actions):
+            remote.send(('step', action))
+        self.waiting = True
+
+    def step_wait(self):
+        results = [remote.recv() for remote in self.remotes]
+        self.waiting = False
+        obs, rews, dones, infos = zip(*results)
+        return np.stack(obs), np.stack(rews), np.stack(dones), infos
+
+    def reset(self):
+        for remote in self.remotes:
+            remote.send(('reset', None))
+        return np.stack([remote.recv() for remote in self.remotes])
+
+    def reset_task(self):
+        for remote in self.remotes:
+            remote.send(('reset_task', None))
+        return np.stack([remote.recv() for remote in self.remotes])
+
+    def close(self):
+        if self.closed:
+            return
+        if self.waiting:
+            for remote in self.remotes:            
+                remote.recv()
+        for remote in self.remotes:
+            remote.send(('close', None))
+        for p in self.ps:
+            p.join()
+            self.closed = True
+
+    def __len__(self):
+        return self.nenvs